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n> I need to setup a Linux Enterprise 5.0 as firewall and router in my
n> network. Please guide me how to do it.

Rather than go through all the hassle why not use Smoothwall and a
switched hub, that's what we have here and it works very well. The box
we use has two NIC's, one goes to the ADSL router and one goes to a 16
port switched hub.

Um, Linux, per se isn't a router - although it can function as one. More, a router is not a firewall, although you can apply basic filtering to a router.

There are some very good firewalls based on linux - Astaro comes to mind. It's free for home/personal use and is affordable for companies, but it's not the only one. Keep in mind that in general a well maintained firewall of almost any kind is better than one set up by someone lacking understanding. The default configuration should be 'block everything', and you (the firewall wizard) will open only the access needed for people to get their work done. As that definition is different for every single business there isn't much beyond 'deny all' that can be set by default, which is why it is critical that you understand what you're trying to do.

If your goal is to learn how Linux does routing and firewalling, then by all means use Linux.

If you goal is to build a fast, stable, secure router with a firewall, use BSD. There are 2 main reasons to choose BSD over Linux for this role.
1. BSD is a more stable OS
2. The BSD firewall packet filter (pf) is much faster and more stable than an ipchains managed Linux Kernal Firewall and unlike Linux, is capable of state full packet inspection.

For a better router, I recommend BSD over Linux. If you want a pre-configured easy to manage via web gui BSD router/firewall, go with pfSense. Otherwise, if all you want to do is learn more about Linux, by all means use it.

Thanks for guiding me to use open source as firewall, i check out on net and found that that Pfsense is good for me to use. (cause it can be handle by web also). but as i said earlyer i am zero (0) in linux. so here my Q are:

can i install it on my redhat linux 5.0 machine ?
how to download and which version to download from net (as i have a 8 GB pendrive)
how to install it on linux machine
how to configure it as router and firewall
in need to block all port except port 80, 443,465,995 etc.

give me some link to check it out (as i never use linux and zero in this feld.

No - all these are designed to be run as stand-alone systems and will
erase any OS currently installed. FWIW - that's the *only* way to
create a secure firewall and ensure that only the bare essential
services are in operation. Trying to do it on a working OS is doomed
to failure and endless configuration headaches - it's not worth it too
as you can never be sure that it's operating correctly.

All you need is a spare PC and it can be low powered one that's not
much use for anything else :-)

n> how to download and which version to download from net (as i have a
n> 8 GB pendrive)

Generally you download the ISO from the maker's web site and create a
bootable CD (or USB drive if that's available) to do the installation.

n> how to install it on linux machine

As mentioned above, you don't install it on any OS - it's an OS all by
itself.

n> how to configure it as router and firewall

Firewall configuration is included in the relevant manuals and you
need to read these before installation as some of the things you need
to know during the install are covered. To act as a router all you do
is fit two network cards - one for the connection to the internet via
your normal router and one goes to a switched hub.

n> in need to block all port except port 80, 443,465,995 etc.

Not a problem, read the installation manual how this is done via the
web interface.

It looks a bit daunting at first if you've never done it but forget
the fact it's a Linux box as everything is done through a browser and
the OS itself is transparent / irrelevant.

pfSense cannot be installed on Linux other than as a virtual machine. It is a custom BSD operating system designed to be used as a router/firewall. Initial setup and configuration is done with a GUI and after installation, management is done via a web based interface. No BSD knowledge is required but learning BSD will help you do more with the device.